Trunk selection arrangement for a line concentrator system



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United States Patent 3 299 213 TRUNK SELECTIQP J AliRANGEMENT 150R ALINE CONCENTRATOR SYSTEM John S. Young, Addison, Ill., assignor toAutomatic Electric Laboratories, Inc., Northlake, Ill., a corporation-This invention relates to data communication systems wherein a pluralityof subscribers share a lesser plurality of trunks for connection to acentral office, and more particularly to the convergent network throughwhich the lines which emanate from the subscriber stations are coupledto a smaller number of trunks at the remote concentrator unit, and tothe divergent network at the central office through which the trunks arere-expanded to an equal number of subscriber line terminations.

It is a general object of this invention to provide an improvedcommunication system wherein a large number of lines may be connected toa central otlice by a small number of trunks.

It is another object of this invention to provide an improved systemwherein a number of subscriber lines may be connected by a plurality offirst crosspoints to a lesser number of trunks, which in turn areconnected to a second plurality of crosspoints to an equivalent numberof line circuits at the central olfice.

The disclosed circuit provides for serving up to 10 station lines via amaximum of trunks. All control functions are via the working or callhandling trunks; no separate control trunk is required.

Each remote station requires line equipment at the central oflice.

The wire transmission facility is switched through a x5 crosspointmatrix at the remote location, and also at the central ofi'ice in orderto effect the concentration of 10 lines to 5 trunks at each end of thesystem.

A common relay group at each end controls the matrix. In the quiescentcondition each marker has pre-allotted an idle trunk; synchronizingmeans are provided so that the same trunk is allotted at each end. Anoriginating call causes the remote marker to outpulse a single digitcorresponding to the number of the calling line. This digit is receivedby the marker at the central oifice end. When the calling line identityhas been transmitted, the matrices are switched and the next idle trunkallotted in preparation for the next call.

Terminating calls are treated in a similar manner, and

the identification digit is transmitted from the central office to theremote location.

Means are provided to place the remote line in lockout and free thetrunk circuit in response to a lock-out indication at the central officeline equipment.

In the exemplary embodiment set forth herein the crosspoint relays areso called reed relays wherein the contacts are sealed in glass envelopeswith the relay winding wound around all of the envelopes of the contactscomprising the relay. A typical reed type relay is disclosed in thecopending application of George S. Lychyk and Arvo Taliste filed July28, 1961, Serial No. 127,648, granted April 7, 1964, as U.S. Patent No.3,128,356. The matrix arrangements of these relays is disclosed in thecopending application of Peter K. Gerlach, George J. David and RudolphO. Stoehr filed August 21, 1961, Serial No. 132,897, granted July 6,1965, as U.S. Patent No. 3,193,731, while the overall system with whichthis disclosure is arranged to operate is disclosed in the copendingapplication of Frank B. Sikorski and Kore K. Spellnes filed December 12,1962, Serial No. 244,058, granted December 28, 1965, as U.S. Patent No.3,226,488.

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A feature of this invention is the use of all of the trunks for thehandling of calls without requiring separate control facilities.

Another feature of this invention is that the concentrator calling linenumber is pulsed from the calling end to the called end prior tocompleting the connection through the concentrator system. L

Still another feature of this invention is that the calling line numberis pulsed out simultaneously with the scanning of the calling linegroup.

The foregoing and other objects and'features. of this invention and themanner-of attaining them will become more apparent and the inventionwill best be understood, by reference to the following description of anembodiment of the invention-taken in conjunction with the accompanyingdrawings, comprising FIGS. 1 to 20, where- FIGS. 1 to 4 disclose thecircuit of the remote end concentrator'common marker. I

FIG. 5 discloses a concentrator trunk circuit for the remote end.

FIG. 6 discloses a concentrator trunk-circuit for the central officeend. I

FIGS. ,7 to 10 disclose the circuit of the central ofiice endconcentrator common'marker. i i

FIG. 11 discloses the remote end subscriber line circuit. 1

FIG. 12 discloses the subscriber lineand line termination relays. Y

FIG. 13 shows in abbreviated form the crosspoint switching matrix forthe remote end.

FIG. 14 shows the remote end trunk terminal equipment and the linetermination relays connected at the trunk side of the matrix.

FIG. 15 shows the central ofiice end trunk terminal equipment and theline termination relays connected at the trunk side of the centralotfice concentrator matrix.

FIG. 16 shows in abbreviated form the crosspoint switching matrix atthecentral office end, and also the line termination equipment.

FIG. 17 shows the line circuit adapter for the central office end of theconcentrator.

FIG. 18 is a block diagram of the-system.

FIGS. 19 'and 20 show how FIGS. 1-17 should be arranged to form aunitary disclosure.

GENERAL Each station line is provided with a line equipment at theremote location, and also with a'regular line circuit at the centralofiice. The central office may be of thegeneral type disclosed in thecopending application of Ivan V. Coleman, Lester L. Smith and Willard A.Rust filed October 24, 1963, Serial No. 318,646. In order that thecentral ofiice line circuit may be assigned among any of the universal16KC equipments, an adapter is provided to associate the regular line tothe special requirements of the concentrator. Theadapter is mounted aspart of the concentrator.

Each trunk requires a relay group at the remote location and at thecentral oflice. A 10x5 crosspoint matrix is provided at each end toswitch connections between lines and trunks.

Control ofswitching functions is provided by'a common relay group whichmay be called a marker. The same concentrator marker is used at both theremote and central office locations.

Concentrator operation requires that a line requiring originating orterminating service be switched to an idle trunk at each end of thesystem. Normally, each marker will pre-allot the same idle trunk.Assuming an originating call, the operation is as follows:

The remote line relay operates to close a start signal to the marker,which in turn closes an off-hook to the central ofiicef If the centraloffice concentrator marker 'is associated with the selected trunk as itshould be, a

wink signal is returned to the remote location to indicate that callset-up may proceed. If the central ofiice marker is not associated withthe selected trunk, a relay finder in the marker finds the callingtrunk, after which the wink is returned.

The remote marker steps a relay scanner to look for the calling line. Atthe first step, a pulse (on-hook) is transmitted to the central otfice.When this is registered in the central ofiice marker, an off-hook isreturned, causing the remote scanner to take another step. This sequence.is repeated until the calling line is found.

' In this manner, an interlocked or revertively pulsed digit transmitscalling number information to the central ofiice. The matrices areswitched when this operation is completed, and the markers disassociatedthemselves from the trunk. When the central office equipment is ready toreceive address information, olf-hook and dial tone will be returned.The off-hook will be maintained for the duration of the call; an on-hookwill cause the remote line equipment to go into lock-out, releasing thetrunk. Supervisory information (including dial pulses) is via lead ECthrough the matrices. The circuit is arranged for the EC lead to be usedfor two-way supervision.

Terminating calls are set up in the same manner as originating, exceptthat the'central ofi-lce concentrator marker performs the scanningoperation. An additional factor on terminating calls is that if theremote line is in lock-out, it will test idle at the central otficetermination since no trunk is held in this case. Accordingly, when thecentral office equipment switches a call to a concentrator line, animmediate hold is returned to prevent the central oflice connector fromringing while the call is being set up to the remote location. If thecalled line tests idle at the remote location, the hold is removed andringing proceeds in the normal manner, but if a lock-out condition isfound, this is signalled back to the central office via a flash. Thecentral office line e.g. adapter then goes into the equivalent oflock-out, releases the trunk, trips the ring in the connector withoutanswer supervision, and returns busy tone to the calling party.

If an originating and terminating call seizes the respective markerssimultaneously, a time-out at the remote location gives preference tothe terminating call.

A time-out on start signals provides an alarm if service is not obtainedthrough the concentrator within 10. seconds.

Thedesign provides that a 48 volt power supply is required at the remotelocation, but not tone or ringing equipment.

Call from the remote end Pre-Seizure.Assume the first high-usage trunkis preallotted, then the following relays are operated at the remote andcentral office ends of the concentrator respectively; 3TM, 3TMS, 4ATB,4DS, SAG, and STM, STMS, 7ATB, 7DS and 6AG. The manner in which theserelays are operated in explained in the section titled TrunkPre-Allotting.

- Sefzurc.-(Operated: Relays 3TM, 3TMS, 4ATB, 4DS, SAG and 6A6) When thesubscriber is otf hook, the circuit to relay is closed over the simplexloopsltown in 12RC. Relay 11L operates, closes lead llPB via the secondwinding of relay 11CO to lead MP1, and grounds lead 11ST to close acircuit to relay 1OT and thermal delay relay lGV. Relay 1OT operates,grounds lead llPB to mark the line requesting service, opens the circuitof relay 3TM, transfers lead lMM from ground to resistance 1L battery,and grounds at contacts 10T7 a lead to close a circuit to relay 5B.Relay 5B operates.

Resistance battery on lead SM is converted to ground by the signalequipment; this ground is applied to leads 6ED and 6E8 at the centralotlice end.

If the central office-concentrator marker is associated with theselected trunk (as it should be), ground on lead GED at the centraloffice end of the concentrator is extended to relay 7DP via lead 6EM.Correed 7DP at the central ofiice end operates and closes a circuit tothe first winding of relay 7EM. Relay 7EM operates and closes circuitsto relay 8EB and the second winding of relay SCT in multiple. Relay 8CToperates and transfers lead 7MM from ground to resistance 10L battery.Relay SEB operates, closes a circuit to the second winding of relay 7DS,and closes a circuit to relay l0l l. Battery on lead 6M at the centralotfice end of the concentrator is converted to ground by the signalequipment and applied to leads SED and SES at the remote end.

Ground on lead SED extends to lead 4EM and closes a circuit to relay4DP. Correed 4DP operates and closes a circuit to the first winding ofrelay 4EM. Relay 4EM operates and closes a circuit to relay SEB. Relay3E8 operates and closes a circuit to the second winding of relay 4DS.

After its slow to operate interval relay 10IN, at the central officeend, operates its X contacts 10lN3, locks, operates fully, opens thecircuit to the second winding of relay 8CT, closes a circuit to relay 6Bvia ground on lead 7B and grounds leads 10PA110. Relay SCT restores andtransfers lead 7MM from resistance battery to ground. Relay 6B operatesand locks to ground on lead 6E8.

Finding the Calling Line-(Operated: Relays at both ends 3TM, 8TM, 4ATB,7ATB, 4DS, 7DS, SAG, GAG, 5B, 6B, 4DP, 7DP, 4EM, 7EM, SEB, 8EB; at theremote end 11L and 10T; and at the central office end IOIN).

Ground on lead 7MM at the central office end is extended to lead 6M.This ground is converted to battery by the signal equipment and appliedto leads SED and SES of the remote concentrator trunk short circuitingrelay 4DP; correed 4DP restores and opens the circuit to the firstwinding of relay 4EM. Relay 4EM restores, opens the circuit of relay3EB, closes circuits to the first winding of relay 3CT and relay 2C1 inseries, and closes a circuit to relay 3CF. Relay 3EB remains operateddue to its slow to release characteristic. Relay SCF operates, closes acircuit to relay 4CB, and recloses the circuit of relay 3TM before itrestores to stop timing. Relay 3CT operates and transfers lead 5MM fromresistance 1L battery to ground. Relay 2CI operates, locks, shunts thesecond winding of relay 3FF, and closes lead MP1 from the line circuitto lead PH of the first horizontal level of the remote switching matrixFIG. 13. Relay 4C8 operates and closes a circuit to the second wnidingof relay 4DS.

Ground on lead SMM is extended to the signal equipment, converted tobattery and applied to leads GED and 6E5 of the concentrator trunk atthe central office end to short circuit 7DP and 6B, respectively.Correed 7DP restores and opens the circuit to the first winding of relay7EM. Relay 7EM restores, opens the circuit to relay 8EB, closes circuitsto the first winding of relay 3CT, 8CT and 9C1 in series, and closes acircuit to relay 8CF. Relay 8CF operates, closes a circuit to relay 7GB,and recloses the circuit to relay STM before it restores to stop timing.Relay 8CT operates and transfers lead 7MM from ground to resistance 10Lbattery. Relay 9CI operates, locks, shunts the second winding of relaySPF, and closes lead 17P1 from the line equipment adapter to lead 16PH1of the first horizontal level of the central ofiice switching matrix.Relay 7C8 operates and closes a circuit to the second winding of relay7DS.

The resistance battery on lead 7MM is extended to the signal equipment,converted to ground and applied to

1. AN AUTOMATIC COMMUNICATIONS SWITCHING SYSTEM INCLUDING: A CENTRALSWITCHING OFFICE, A PLURALITY OF SUBSCRIBERS'' LINES, A PLURALITY OFTRUNKS FEWER IN NUMBER THAN SAID LINES FOR CONNECTING SAID LINES TO SAIDOFFICE, REMOTE SWITCHING MEANS FOR CONNECTING SAID LINES TO SAID TRUNKS,A FIRST PLURALITY OF LINE TERMINATIONS IN SAID CENTRAL OFFICE INDIVIDUALTO SAID LINES, A SECOND PLURALITY OF LINE TERMINATIONS INDIVIDUAL TOSAID LINES FOR CONNECTING SAID LINES TO SAID REMOTE SWITCHING MEANS,CENTRAL SWITCHING MEANS FOR CONNECTING SAID FIRST PLURALITY OF LINETERMINATIONS TO SAID TRUNKS, REMOTE AND CENTRAL CONTROL MEANS CONNECTEDTO SAID REMOTE AND CENTRAL SWITCHING MEANS FOR OPERATING SAID SWITCHINGMEANS, SELECTING MEANS IN EACH OF SAID CONTROL MEANS FOR SELECTING ANIDLE ONE OF SAID TRUNKS, START MEANS IN EACH OF SAID CONTROL MEANS UNDERTHE CONTROL OF ONE OF SAID LINE TERMINATIONS AT SAID SUBSCRIBER LINES TOINITIATE THE OPERATION OF SAID CONTROL MEANS TO STEP A LINE SELECTEMEANS TO A FIRST STEP TOWARD SAID LINE TERMINATION, SELECT MEANS AT SAIDCENTRAL SWITCHING OFFICE, SYNCHRONIZING MEANS, SAID SYNCHRONIZING MEANSCOMPRISING A FIRST CIRCUIT MEANS AT SAID REMOTE LINE SELECT MEANS TOCOMPLETE A STEPPING CIRCUIT TO SAID SELECT MEANS AT SAID CENTRALSWITCHING OFFICE AND OPEN ITS OWN CONTROL MEANS, SAID LAST MEANSREMAINING OPEN UNTIL SAID CENTRAL OFFICE SELECT MEANS COMPLETES ACORRESPONDING STEP, AND SECOND CIRCUIT MEANS AT SAID CENTRAL OFFICESELECT MEANS TO OPERATE SAID FIRST CIRCUIT MEANS TO RECLOSE, SAIDSTEPPING ALTERNATELY OPERATED TO STEP A CORRESPONDING LINE TERMINATIONAND A CONNECT CONTROL MEANS THEREAFTER OPERATED TO OPERATE SAIDSWITCHING MEANS TO CONNECT SAID LINE VIA SAID SELECTED TRUNK AND SAIDTWO LINE TERMINATION EQUIPMENTS TO SAID CONTROL SWITCHING OFFICE.